I would prefer Centenera as the first climb to Pedro Bernardo - it would also make a double cat.1 opening. The alternative would be to go straight to Serranillos from the word go, making it a full cat.1 climb (plus also harking back to Bernard Hinault's great 1983 show that won him the race in the Ávila stage), then La Erilla and Las Erillas back to back before Chía and Peña Negra.
Last year they climbed the easier side of Peña Negra in the La Covatilla stage. The last time they climbed this side was 2004, in the Ávila stage. Juan Fuentes won the climb from the early break, Javier Pascual won the stage in a two-up against Iván Parra. Typically the climb has been used as part of intermediate stages into Ávila like that, going over Peña Negra early, then over rolling terrain through the Sierra de Gredos, descending through the Puerto del Pico and ascending the Puerto de Serranillos. Laurent Jalabert won a 1995 stage of that fashion, from Salamanca, taking the Peña Negra summit en route despite already being in the race lead. The 1995 stage was a clone of a stage which had in fact been used three times before, and it was the third time in four years that an almost identical stage design had been used, after 1992 and 1993. The reason for the repetition, however, was an attempt to ape Bernard Hinault's legendary attack in 1983 that was part of what cemented Ávila's place of legend in the Vuelta long before Frank Vandenbroucke had even considered it. Hinault was a bit of a wounded animal at that point in the 1983 race, having taken the lead on stage 5 but lost it a day later having been caught out in the Pyrenees. Suffering from tendinitis, he also lost time in the Panticosa TT at the midway point, and while he'd gained some time back on Gorospe and Fernández at Lagos de Covadonga, he'd lost it to Marino Lejarreta. Also growing suspicious of his young teammate Laurent Fignon, the always belligerent Badger won the stage 15 ITT but was still just over a minute off the lead going into the penultimate decisive stage. He attacked hard on Peña Negra, well over 100km from home, and isolated the other leaders, before disappearing once and for all on the Puerto de Serranillos. He was not keen on being upstaged, regardless of the consequences, and the Badger felt he was being humiliated in Spain against opposition he ought to have stomped. Tendinitis be damned, he rode his heart out to prove his point, and while eventually Lejarreta and Belda joined him, he took the stage and turned his disadvantage into a clear lead, with the trio finishing three minutes up on anybody else - with Fignon leading the second group.
Of course, as well as being one of the Vuelta's most legendary stages, comparable in lore to Fuente's legendary Formigal raid, Loroño being wrestled off his bike on the snowy Puerto de Pajáres, and in latter years Heras' Pajáres masterstroke and Contador's Fuente Dé escapades, that stage also paved the way for the next phase of cycling history, with the effects of riding on through the tendinitis to prove his point causing Hinault to miss the Tour de France; that led to Renault-Elf putting their weight behind Fignon, who won the Tour and set in motion the rivalry that would characterise the next few years. 1983 is probably the only time that Peña Negra has really played a central role in proceedings, despite being over 100km from the finish, due to the Badger's determination that ultimately cost him dearly, despite winning him what is still considered one of the greatest Vueltas ever raced, tomorrow is probably its best chance since then to pave itself into the race's lore.